WASHINGTON — It’s official: The National Institutes of Health plans to end most use of chimpanzees in government medical research, saying humans’ closest relatives “deserve special respect.” The NIH announced today that it will retire about 310 government-owned chimpanzees from research over the next few years, and keep only 50 others essentially on retainer — available if needed for crucial medical studies that could be performed no other way. “These amazing animals have taught us a great deal already,” said NIH Director Dr. Francis Collins. He said the decision helps usher in “a compassionate era.” The NIH’s decision was long expected, after the prestigious Institute of Medicine declared in 2011 that nearly all use of chimps for invasive medical research no longer can be justified. Much of the rest of the world already had ended such research with this species that is so like us. Any future biomedical research funded by the NIH with chimps, government-owned or not, would be allowed only under strict conditions after review by a special advisory board. In five years, the NIH will reassess if even that group of 50 government-owned apes still is needed for science. “This is an historic moment and major turning point for chimpanzees in laboratories, some who have been languishing in concrete housing for over 50 years,” said Wayne Pacelle, president and CEO of The Humane Society of the United States. “It is crucial now to ensure that the release of hundreds of chimpanzees to sanctuary becomes a reality.”